I have a still image that I want the frame to slightly pan from left to right.
For example, the image is 1920x1080 and the actual viewing area is 1280x720 with the rest of the image unseen in the background.
I want to have the viewable area track from left to right a little bit just to give a panning effect.
Keyframe animation (which is what you need for this project) is one of the very basic first steps to learn when working with After Effects. I highly suggest you either start here or start here and learn these basics before you try to go any further in AE.
Before that, another basic building block is creating compositions. You need to make one that's 1280x720.
And another basic skill is importing assets and footage (another basic building block), but I'm assuming you've figured this part out.
Basically, you need to animate either the position or the anchor point of your picture layer.
Keyframe animation, got it, thanks for pointing me in the right direction